Tube exploded while filling!
So, I put a brand new tube into my tire. Filled it up to about 20 psi. Checked the rim all around. Bead was securely in the rim on both sides. White stripe around tire was even to the rim all around. So then I continued to fill it with my electric pump.
My tires (Schwalbe Marathon Plus) have a max of 60 psi, which I always fill it to without problems. However, I was a little past 55 psi when I heard a loud "bang" and all the air gushed out.
Looking at the tube, it was torn open by about a foot on each side of the valve.
Any idea what could have caused it?
I will say that I was going to add sealant to it, but I couldn't get the valve core out. Even used a metal tool, rather than a plastic one. But the tool wouldn't go all the way down into the stem, like something was stuck in there. However, the tube was able to receive air, so I decided to fill it up and ride with it until I could get a new tube.
Puzzling.